1. Field of the Invention
This invention relates in general to photographic printers and copiers intended for exposing light-sensitive material to an original and making a photographic likeness thereof. More particularly, the invention provides a transport apparatus for supporting and guiding an element, bearing an original image, that moves by its own weight through operative stations in a printer or copier and, yet more particularly, includes apparatus for aligning the element in a printing station.
2. Description of the Prior Art
Inasmuch as the invention has particular utility in the field of photographic printers, the description relative to the prior art will be couched in such terms. However the need to cast the invention in terms of particular apparatus does not diminish its importance in the area of sheet transport generally. In fact the description here provided for use in photographic printing also illustrates the advantages of gravity guided transport generally.
The problem of transporting and then orienting original material in a photographic printer has typically resolved into two companion situations. On the one hand, original material--such as photographic negatives--has been joined together in lengthy strips which are advanced through the printer for individual exposure with varying degrees of operator assistance. On the other extreme, when faced with odd-sized material or originals not capable of convenient joining, the printer operator manually positions each piece of original material before making an exposure. The latter situation is less desirable for its related impact on productivity and labor costs.
With the introduction of copy materials adapted for direct exposure to the customer print itself--rather than to the photographic negative--photo processors and printers need to provide for volumes of single prints delivered to them for duplication. In some cases single customer prints are the only practical originals, e.g., prints developed from instant processing film packages since the negative is not readily recoverable for purposes of duplication. Furthermore, joining single pieces of original material into lengthy strips for automated printing may be time consuming and expensive and additionally involves the risk of damaging the original print. Unlike negatives, original prints are not only returned to their owner but are subject to the more critical scrutiny deserving a finished product since the originals themselves are images suitable for viewing, mounting, framing, etc. Therefore the need exists for a simple transport apparatus disposed to efficiently handle large volumes of single originals carefully and inexpensively, while also accurately and repeatedly positioning each original in a printing gate for exposure to light sensitive photographic material.
Registration of an original in the printing gate of a photographic printer should be precisely controlled if the duplicate image is to be squarely positioned and framed relative to the edges of the light-sensitive copy paper. Since the copy paper is typically provided in roll form and automatically unwound and positioned frame-by-frame in a predetermined location in the optical axis of the printing mechanism, the full realization of image alignment rests with the original element and the manner in which it is positioned at the printing gate.
Registration of individual pieces of original sheet material is conventionally performed by manual assistance or by involved transport apparatus. Manual registration, as the permanent recourse, is unsuitable for reasons of productivity and labor expense. Automatic transport apparatus typically involves conveying systems that operate in two dimensions--one to shove the material into the gate until stopped and another to force the material transversely into an aligning position. Besides the complexity, such apparatus becomes massive when space is at a premium in the machine. Other devices based on hydraulic or fluidic positioning possess similar drawbacks.